Crime: After a call, officers stake out a Mission Viejo park to watch her arrive. A search of her home yields journals and sharp objects.

It was usually dark when Lori Elizabeth Fischer ended her shift as a filing clerk for a temp agency. The 21-year-old cruised the curving greenbelts of south Orange County in her silver sedan, stopping for walks at the small parks carved out amid the rambling red-tile roofed subdivisions.

She told friends that walks helped clear her head and relax. But authorities allege that over the last two months, Fischer meticulously planted razor blades, nails and other sharp objects in strategic locations at parks, buried in sandboxes and under slides and swings.

Before many of the incidents, Fischer called police from pay phones, sometimes using the name "Danni," to warn them of cities about to be targeted, Orange County sheriff's officials said Wednesday. She allegedly kept newspaper clippings of the discoveries and filled a thick journal with musings and poems about the wave of razor-blade findings that set area parents and children on edge.

One of her verses, provided by the Sheriff's Department, read: "Nature's most precious resource / Frolics in the sand / Not a care in the world / Just unending joy / All is shattered / When the authorities come / Beep, Beep, Beep / Shiny, sharp objects in the sand / Of a child's playground / Who would do it / Who would hurt an innocent."

A day after Fischer's arrest, her friends and former teachers Wednesday were asking that very question. Some described her as a quiet but intense person. She was a loyal friend, they said, someone incapable of the crimes she is accused of committing.

But others said she was lonely and depressed. At Capistrano Valley High School, where she graduated in 1998, Fischer was often seen walking campus corridors alone with a pet lizard on a leash.

"She was eccentric, and she wasn't the picture-postcard California teenager," said Lyn Harvey, who taught her academic decathlon for three years. Others recalled that Fischer regularly sought attention, often staying after class to talk to instructors.

"She was a needy student who would act out in various ways," said Stan Nickel, her choir teacher in junior year. "I could see where she had the need to be something or at least be recognized.

"I was shocked to see her face [on television] but not surprised," he added.

Neighbors in the Mission Viejo block where Fischer and her parents lived said they often heard Fischer screaming at night from inside the home.

Prosecutors said Wednesday that they plan to charge Fischer today with felony counts of assault with a deadly weapon and willful intent to injure a child. Authorities found sharp objects at 10 parks in Orange County, and Wednesday laid out for the first time what led them to believe Fischer is behind the crime spree.

Detectives zeroed in on Fischer two weeks ago, just as alarm over the discoveries reached a peak. Investigators had already talked to her while following vague leads, but the young woman didn't become a suspect until May 23.

That night, deputies staking out Joyner Park in Mission Viejo said they noticed Fischer making a late-night visit. No sharp objects were found at the park, but detectives took her in for questioning.

Sheriff's deputies and Laguna Beach investigators interrogated Fischer three more times. During one of those interviews, they said, Fischer failed a voice stress test--which, like a polygraph, is designed to detect deceit.

The next day, deputies said, they secretly watched Fischer leave work at the Immigration and Naturalization Service in Laguna Niguel about 11:30 p.m., then followed her as she drove to parks in Mission Viejo and Foothill Ranch.

"She didn't stop," sheriff's Sgt. Jim Sewell said. "She'd slow down and speed up and made U-turns. She drove for hours going nowhere and everywhere."

At the same time, the anonymous phone warnings from "Danni" stopped. Fischer began calling the police using her own name, sheriff's officials said, saying that she had heard rumors that a particular city was about to be the next target.

Investigators had a list of 20 possible suspects, but Fischer was moved to the top. Detectives said they attached a tracking device to her car, hoping to catch her in the act.

On Sunday, more than 30 razor blades were found hidden in Alicia Park in Mission Viejo. Had Fischer been there, the tracking device should have recorded her visit to the park. But the device malfunctioned.

On Monday afternoon, Fischer called to tell deputies that she had heard that sharp objects were about to be planted at a park between Vista del Lago in Mission Viejo and Alicia Parkway. Shortly after midnight, a team of undercover sheriff's deputies arrived at Vista del Lago Park. The deputies swept the park for sharp objects and found nothing. About 12:45 a.m., the surveillance team said they spotted Fischer.

Authorities said she spent seven minutes at the park before returning to her car. Deputies who rushed to the park found nails sprinkled on the playground.